The present invention relates to cardiac pacemakers. More particularly, the present invention relates to a shielded cardiac pacemaker enclosure.
In a normal heart, an electrical stimulus is generated within the right atrium and is transmitted to the ventricle where it produces a contracting or beating of the ventricle. However, heart disease can obstruct the normal conduction of the electrical stimulus within the heart and cause the heart to stop beating at its normal rate. Such a condition results in an array of maladies ranging from fatigue to death.
Cardiac pacemakers have largely alleviated this problem by monitoring the electrical activity of the heart itself and detecting conditions in which the electrical stimulus of the heart is inhibited. When such a condition is detected, the cardiac pacemaker takes over and stimulates the heart in a relatively normal manner until the electrical stimulus regains effective conduction.
In order to sense the minute electrical signals of the heart, the cardiac pacemaker must employ sophisticated, sensitive circuitry. As a result, such circuitry is susceptible to radio frequency interference.
Additionally, radio frequency signals are a ubiquitous part of everyday life. Such signals are generated from overhead power lines, fluorescent lights, microwave ovens, and cellular telephones, to name but a few. Although the human body is able to shield an implantable pacemaker from some forms of radio frequency signals, all pacemakers (both implantable and external) to some degree may be affected by such signals. Thus, a pacemaker may be caused to falsely sense the condition of the heart resulting in inappropriate pacemaker action.